Let getContentHeight be used from any thread

Fix for bug 10594869

Change-Id: I94c9840811abb207c23db8816f2e282e7807c746
diff --git a/chromium/java/com/android/webview/chromium/WebViewChromium.java b/chromium/java/com/android/webview/chromium/WebViewChromium.java
index f1343c0..4469189 100644
--- a/chromium/java/com/android/webview/chromium/WebViewChromium.java
+++ b/chromium/java/com/android/webview/chromium/WebViewChromium.java
@@ -547,7 +547,7 @@
 
     @Override
     public int getContentHeight() {
-        checkThread();
+        // No checkThread() as it is mostly thread safe (workaround for b/10594869).
         return mAwContents.getContentHeightCss();
     }